1. Field of the Invention
The present invention relates to a brush assembly of an alternator for a vehicle, and more particularly to brush and holder assemblies having improved configurations in accordance with improvements in brushes serving as connecting means contacting a slip ring to supply magnetization current to a rotor coil, springs, lead wires, and terminals, and thus an improvement in reliability.
2. Description of the Related Art
In vehicles, an alternator is used as an important electrical device of an engine. Such an alternator is connected to an engine via a belt to generate electricity, thereby charging a battery while supplying, to other electrical devices, current required to operate those electrical devices. Alternators for vehicles mainly include a stator assembly interposed between a slip ring and a driver end frame, and a rotor assembly arranged inside the stator assembly, and supported by a rotor shaft.
The rotor shaft, which is included in the rotor assembly, is connected with a rotor coil at a rear end thereof. A slip ring is fitted in a rear end of the rotor shaft included in the rotor assembly. The slip ring is a terminal connected to the rotor coil while being mounted to the rotor shaft of the rotor assembly. A brush assembly comes into contact with the slip ling in order to supply magnetization current to the rotor coil.
Generally, the brush assembly has an integrated construction including a pair of brushes made of high-density carbon or carbon alloy, and received in a brush holder molded in accordance with an injection molding process. This brush assembly is assembled separately from other elements included in the alternator, and then fitted in the alternator.
Also, a regulator is assembled, as a separate integral element, in the alternator in order to maintain the voltage generated from the alternator to be at a desired level, so that it forms an electrical device.
The brush assembly includes wired brushes typically made of carbon received in a brush holder. The wired brushes are always urged against the slip ring on the rotor shaft by springs assembled in the brush assembly so that they perform a connection to the slip ring.
FIG. 1 is a sectional view illustrating a conventional alternator for vehicles. FIGS. 2A and 2B illustrate different states of wired brushes received in a brush assembly included in the alternator of FIG. 1, respectively. FIG. 3 illustrates the brush assembly.
As shown in FIG. 1, the conventional alternator, which is denoted by the reference numeral 10 in FIG. 1, includes a stator assembly 15 fitted in a space defined between a driver end frame 11 and a slip ring end frame 12. The stator assembly 15 consists of a stator core 13, and a stator coil 14. A rotor shaft 17 is freely rotatably mounted to the driver and slip ring end frames 11 and 12 by bearings 16 fitted in central portions of the driver and slip ring end frames 11 and 12. The rotor shaft 17 is provided at one end thereof with a pulley 17xe2x80x2 for power transmission.
A spool bobbin 20 is fitted around a middle portion of the rotor shaft 17. A rotor coil 18 is wound around the spool bobbin 20 while being connected with a slip ring 19 arranged near the other end of the rotor shaft 17. Rotor cores 21 and 22 are coupled to the spool bobbin 20 around the spool bobbin 20. The rotor core 21 has a plurality of rotor poles 23, whereas the rotor core 22 has a plurality of rotor poles 24. Thus, a rotor assembly 25 is formed. A brush assembly is formed by wired brushes 1 arranged around the slip ring 19, and connected to the rotor coil 18 in order to supply current to the rotor coil 18. A regulator R is arranged at one side of the brush assembly.
As shown in FIGS. 2A and 2B, each of the wired brushes 1 is assembled separately from the remaining wired brushes 1, and then received in the brush assembly B. Each wired brush 1 includes a bar-shaped brush body made of a material such as high-density carbon or carbon alloy while having a rectangular cross-sectional shape, and a lead wire 3 fixed at one end thereof to the brush body 2 in accordance with a tamping process, and protruded from the brush body 2. The other end of the lead wire 3 is fixed to a terminal 4 receiving current, by means of a weld 5.
A spring 6 is fitted around the lead wire 3 in order to maintain the brush body 2 to be in contact with the slip ring 19. A sleeve 7 is coated over the lead wire 3 in order to prevent the lead wire 3 from being damaged by the spring 6.
Since the lead wire is fixed to the brush body by tamping, the above mentioned conventional configuration exhibits a low electrical conductivity, thereby causing a high voltage drop, and generation of heat. For this reason, the amount of supply current is reduced, thereby adversely affecting the performance of the alternator. Furthermore, since the sleeve should be coated around the lead wire, an increase in the manufacturing cost occurs. In addition, the wired brush has a degraded durability because the lead wire portion welded to the terminal is weak.
The conventional alternator involves a serious problem, for example, a jamming phenomenon, caused by its configuration during the procedure in which the brushes are extended and retracted. That is, the lead wire may be broken or mechanically caught by the spring as the lead wire arranged inside the spring is repeatedly bent or folded in accordance with the repeated extension and retraction of the brush. In severe cases, the brushes cannot be normally operated. That is, a so-called xe2x80x9cjamming phenomenonxe2x80x9d may occur. In addition, powder produced due to an abrasion of carbon brushes, dust, and other foreign matters may be introduced into slots where springs and lead wires of respective brushes are received. In this case, there is a high possibility that the lead wires, springs, and sleeves may adhere to one another due to such dust.
Therefore, an object of the invention is to provide a reliable brush assembly with a high quality improved over the related art.
In accordance with one aspect, the present invention provides a brush assembly of an alternator for a vehicle comprising a brush holder including a hollow brush holder body, and a pair of wired brushes each received in the brush holder, and adapted to be urged against a slip ring fitted around a rotor shaft by a spring along an axis of the slip ring, thereby coming into elastic contact with the slip ring to obtain an electrical connection to an external electrical device, each of the wired brushes consisting of a brush, and a lead wire electrically connected to the brush, wherein: the brush holder body of the brush holder has a pair of brush channels each adapted to receive the brush of an associated one of the wired brushes, and a pair of wire channels each arranged at one side of an associated one of the brush channels while extending longitudinally in parallel to the associated brush channel and communicating with the associated brush channel; and the brush of each wired brush is received at one end thereof in an associated one of the brush channels, and elastically supported by the spring associated with the wired brush while being electrically connected with the lead wire of the wired brush at the one end thereof.
In accordance with another aspect, the present invention provides a brush assembly of an alternator for a vehicle comprising a brush holder including a hollow brush holder body, and a pair of wired brushes each received in the brush holder, and adapted to be urged against a slip ring fitted around a rotor shaft by a spring along an axis of the slip ring, thereby coming into elastic contact with the slip ring to obtain an electrical connection to an external electrical device, each of the wired brushes consisting of a brush, and a lead wire electrically connected to the brush, wherein: the brush holder body of the brush holder has a pair of brush channels each adapted to receive the brush of an associated one of the wired brushes, and a pair of wire channels each arranged at one side of an associated one of the brush channels while extending longitudinally in parallel to the associated brush channel and communicating with the associated brush channel; and the brush of each wired brush is received at one end thereof in an associated one of the brush channels, and elastically supported by the spring associated with the wired brush while being electrically connected with one end of the lead wire of the wired brush at the one end thereof; and further comprising: terminals mounted to an end of the brush holder body disposed near the other ends of the lead wires in the wired brushes, and connected to respective other ends of the lead wires by welding, the terminals having connection taps, respectively; an insert terminal formed to be integral with a regulator included in the alternator while having a plate shape, the insert terminal extending inwardly into the brush holder body at the end of the brush holder body while having, an inner end thereof, terminal taps adapted to be coupled with the connection taps of the terminals by welding, respectively; and a brush holder cap adapted to cover the end of the brush holder body.